Again, I apologize for not having the ability to look at the control panel. But I seem to remember three switches, one being tank levels, the second being battery level, and the third being water heater. But the panels may have changed since ours was built. Looking at the photo of your water heater, I would expect to see an electrical element fitting and the associated wiring for the heater element. I don't see anything different from my memory of our heater. Could it be possible that the switch for the electric water heater that is on your panel is in fact a battery capacity switch, but has been labeled wrong. If it is not a battery capacity switch, can you find that switch anywhere else? Sorry, but I am grasping at straws here.